1. Field of the Invention
The present invention relates to a variable valve for controlling the flow of fluid, and more particularly, to a leaf spring type variable valve which maintains a strong spring characteristic regardless of surrounding environment and prevents waste of design space by installing a leaf spring to have an area in contact between a leaf spring support part fixedly engaged to a housing which has an opening and a valve cover which opens and closes the opening.
2. Description of Related Art
The variable valve in general is used so as to control the flow of fluid such as liquid and gas. Such a variable valve operates in such a manner to open or close a valve cover (gate) depending on the pressure of fluid.
As one example of the use of such a variable valve, there is a circular plate type variable valve installed at a muffler of an exhaust system of a vehicle.
The exhaust gas combusted inside of a vehicle engine has a very high temperature and a speed which is nearly like the velocity of a sound. When such exhaust gas is directly discharged into the air, the exhaust gas quickly expands which generates a sound like a big explosion. For this reason, a muffler is additionally installed at an exhaust gas passage of a vehicle in order to reduce the noise of exhaust by lowering the temperature and pressure of the exhaust gas.
The muffler in general is formed in a shape of a cylinder with a predetermined size. Pluralities of pipes and baffles are installed inside of the muffler so as to reduce the exhaust noise by guiding the expansion, resonance and sound absorption of the exhaust gas when the exhaust gas flows.
The above muffler has a problem wherein when the exhaust resistance is increased to reduce the exhaust noise, the resistance applied to the exhaust stroke is specifically by increasing the back pressure which also decreases the engine output, and on the other hand, when the exhaust resistance is decreased to prevent the loss of the engine output, the exhaust noise increases.
In order to improve the above-mentioned problems, a variable valve attachment type muffler is developed and used, wherein the variable valve is installed inside of the muffler so as to decrease the back pressure while driving over middle and high speed sections where the engine output becomes problematic, but increase the back pressure while driving over a low speed section where the exhaust noise occurs.
FIG. 1A is a perspective view illustrating a configuration of a conventional variable valve and FIG. 1B is a perspective view illustrating a configuration wherein a valve cover is removed from the conventional variable valve.
Referring to FIGS. 1A and 1B, the conventional variable valve is characterized in that a housing 1 having an opening 1a is secured to one of the baffles which form a wall surface partitioning the inside space of the pipe or the muffler installed inside of the muffler (not illustrated), and a valve cover 2 is rotatably secured to the housing 1 to open and close the opening 1a of the housing 1.
The valve cover 2 is installed to be rotatable about a shaft 3a secured to one side of the housing 1 wherein the shaft 3a functions as a rotary shaft. A torsion spring 3 is inserted into the shaft 3a wherein one end of the torsion spring 3 contacts with the valve cover 2 to thereby elastically pressurize the valve cover 2.
The thusly constituted variable valve is operated such that when the pressure of the exhaust gas becomes more than the elastic force of the torsion spring 3, the valve cover 2 is opened, and when the pressure of the exhaust gas is smaller than the elastic force of the torsion spring 3, the valve cover 2 remains closed.
In other words, such a variable valve is closed at a low speed section, so that low frequency noise is reduced, and at the middle and high speed section, the variable valve is gradually opened, so that high frequency noise is attenuated and simultaneously, the resistance of the exhaust gas is decreased, so that the engine output is not influenced at all.
The conventional variable valve however has problems wherein the precise flow control is impossible because the spring characteristic significantly decreases under the use environment above a predetermined high temperature, and the valve is opened wider than a design value, thus causing an interference with surrounding components.
Since the conventional variable valve has problems wherein since one end of the torsion spring 3 simply has a point contact so as to support the valve cover 2, the behavior of the valve cover 2 is not strongly supported, so that some unpleasant sound occurs due to the shaking of the variable valve itself In addition, some unpleasant touching sound also occurs due to the collision between the valve cover 2 and the housing 1 when closing the valve cover 2.
Referring to FIG. 1B, the conventional variable valve is trying to prevent the unpleasant touching sound between the valve cover 2 and the housing 1 by securing a cushioning member 4 made from a SUS MAT material at the inner circumferential surface of the opening 1a of the housing 1, which leads to the increased manufacturing cost and weight.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.